The group has been dispatching glitter-filled letters to politicians as part of what it calls a "glitter protest".

The MP said the letter went unopened but "clearly had a powder-like substance inside".

On his Facebook page, Mr Laundy vented his frustration at GetUp! while praising the work of emergency services.

"I'm all for organisations making contact with me, but to send any undeclared substance through the mail to the office of a Member of Parliament will inevitably cause alarm and divert important police and emergency services from their critical work," he said.

"Thank you to Burwood LAC - NSW Police Force for their outstanding effort in undertaking a professional response to a grossly irresponsible act."

The incident could have been much worse -- if the letter was opened, the MP would have been finding it in his hair, clothes and carpet for months.

GetUp! sent the letters to 99 MPs who blocked a free vote on same-sex marriage. Mr Laundy's office is the only one to have needed emergency assistance.

GetUp! hasn't escaped unscathed though, at least one MP fought fire with fire, sending the sparkles back to the GetUp! HQ.